Conventionally, as illustrated in FIG. 7, for an air flow measuring device 100, there is proposed a device that includes a housing 102 that defines a bypass flow passage which takes in a part of air (mainstream) flowing inside a duct 101, and a temperature sensor component 103 for measuring temperature of intake air flowing inside the duct 101 outside the housing 102. The air flow measuring device 100 includes a fitted part 107 fitted into an attachment hole 106, and the device 100 further includes the housing 102 and the temperature sensor component 103 which extend on one end side of the fitted part 107. The temperature sensor component 103 includes a terminal 108 extending on the one end side of the fitted part 107, and a temperature detecting element 109 electrically connected to the terminal 108.
The air flow measuring device 100 is set by being inserted into the duct 101 through the attachment hole 106. The one end side is a front end side of the device 100 in an insertion direction at the time of the insertion of the air flow measuring device 100 into the duct 101 through the attachment hole 106. A connector part 111 projecting out of the duct 101 is provided on the other end side of the fitted part 107. Therefore, the air flow measuring device 100 is inserted into the attachment hole 106 from the other end side, and as a result, the device 100 is set on the duct 101, with the fitted part 107 fitted into the attachment hole 106 and the connector part 111 projecting outward of the duct 101.
At the time of the insertion of the housing 102 into the duct 101, the temperature sensor component 103 (the temperature detecting element 109 and the terminal 108) may be brought into contact with the duct 101, and the temperature sensor component 103 may thereby be damaged. Accordingly, technologies of providing a protection member 112 around the temperature sensor component 103 or around the temperature detecting element 109 are proposed for a technology for preventing the contact of the temperature sensor component 103 with the duct 101. See JP-A-2010-185793 and JP-A-2011-085542 corresponding to US2011/0088464A1.
However, most protection members 112 project outward of the housing 102, and with respect to the mainstream in the duct 101, the protection member 112 becomes an obstacle projecting into a passage of the duct 101. Consequently, a pressure loss of the mainstream may be increased.